Historically, power companies use large generators to provide alternating current (AC) power to the power grid. Traditionally, most generators are 3-phase sinusoidal AC designs for a 3-phase AC fixed frequency power grid. Even for applications where DC power is required, 3-phase AC generator is used, which requires a 3-phase rectifier to convert the AC power to DC power. If a simple passive diode rectifier is used, it introduces significant harmonic currents which cause rotor losses and torque ripples. Also, a simple rectifier does not provide the capability of regulating torque and voltage. Other the other hand, an active rectifier requires pulse width modulation (PWM) switching. Wind-powered generators also use active rectifiers. In a typical wind-powered generator, the generator must adapt to varying wind conditions, which lead to varying rotor speeds. In order to maximize power output under a variety of wind conditions, wind generators perform maximum power point tracking (MPPT) by regulating electromagnetic torque through PWM switching. Active rectifiers are more costly, less efficient, and less reliable than passive or half controlled rectifiers, however. Multiphase winding electric machines allow passive rectifiers to be used without introducing excessive torque ripple and rotor losses to the machine, but at a cost of reduced capability of torque and voltage control. For this reason, the usage of simple rectifiers is normally limited to field-wound synchronous machines and fixed speed operation.
Thus, each approach has disadvantages. Active rectifiers are more costly, less efficient, and less reliable than passive and half controller rectifiers, but provide the capability of regulating torque and voltage.
Accordingly, in light of these disadvantages, there exists a need for methods and systems for an integrated electrical generator with hybrid rectifier.